1. Technical Field
The present invention relates to a robot.
2. Related Art
In the related art, a robot having a base and a plurality of arm link portions is known (for example, refer to JP-A-10-100085). Each arm link portion is rotatably coupled to an adjacent arm link portion on a base end side via a joint portion, and the arm link portion closest to the base side is rotatably coupled to the base via another joint portion.
In such a robot, the rigidity of the joint portion that couples the base and the arm link portion or the rigidity of the joint portion that couples the arm link portions together is low as compared to the base or the arm link portions that are biased by the spring elements of the joint portions. As such, a vibration may be easily generated in the arm link portions due to the rotation of the arm link portions or a disturbance applied to the arm link portions.
Thus, in the robot described in JP-A-10-100085, an acceleration sensor is installed at a tip portion of the arm link portion closest to a tip side of the robot, compensation components of the respective joint portions that compensate command values to the motors of the respective joint portions so as to suppress the vibration generated at the tip portion of the arm link portion closest to the tip side are calculated on the basis of the acceleration detected by the acceleration sensor, and the calculated compensation components of the respective joint portions are subtracted from the command values of the corresponding respective joint portions.
However, the robot described in JP-A-10-100085 has the following problems.
Since the acceleration sensor is installed at the tip portion of the arm link portion closest to the tip side, the acceleration detected by the acceleration sensor is converted and corrected for the respective joint portions. At this time, since it is necessary to perform a coordinate axis transformation referred to as the Jacobi's transformation, and a matrix calculation having a number of sine and cosine factors is required, the amount of calculations becomes huge. Since it is necessary to calculate the factors according to the rotation angles of the motors of the respective joint portions that change every moment, it is always necessary to execute huge calculations. Accordingly, there is a drawback in that the response speed becomes slow.
Additionally, since accurate acceleration or speed cannot be fed back if the calculation precision declines, the vibration suppression capability may decline or control performance may be impaired. For this reason, there is a restriction on the design of a control system in that a high-speed computing unit is required, for example.
Additionally, in the calculation of the coordinate axis transformation, there is a region (an incalculable region) with no coordinate axis transformation solution referred to as a singular point. In this region, the vibration suppression capability may decline or the vibration may be increased instead.